package n1004;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.text.DecimalFormat;

public class Main {

	public static void main(String[] args) throws Exception {
		
		BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));
		
		float sum=0.000f;
		
		for(int i=0;i<12;i++)
		{
			sum+=Float.parseFloat(bf.readLine());
		}
		
		
		DecimalFormat df=new DecimalFormat("$0.00");
		
		System.out.println(df.format(sum/12));
		
		
		
	}

}
